Enhanced GMR magnetic head signal through pinned magnetic layer plasma smoothing

ABSTRACT

A magnetic head including a spin valve sensor having a sensor layer stack that includes a pinned magnetic layer, a spacer layer formed on the pinned magnetic layer, and a free magnetic layer formed on the spacer layer. In a preferred embodiment the spacer layer is comprised of CuO x . Plasma smoothing of the upper surface of the pinned magnetic layer is conducted prior to depositing the spacer layer, and a preferred plasma gas is a mixture of argon and oxygen.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to spin valve sensors formagnetic heads, and more particularly to plasma smoothing of the pinnedmagnetic layer surface of a spin valve sensor structure.

[0003] 2. Description of the Prior Art

[0004] Magnetic heads for hard disk drives typically have a read headportion including a magnetoresistive (MR) spin valve sensor structurefor reading data from the disk of the hard disk drive. As is well knownto those skilled in the art, such MR sensor structures include aplurality of thin film layers disposed between two magnetic shields thatdefine the read gap. The thin film layers have particular magneticproperties, and are sensitive to the magnetic field of the data bits onthe hard disk.

[0005] The thin film layers of a typical MR spin valve sensor willinclude at least one antiferromagnetic layer, at least one pinnedmagnetic layer, a spacer layer and at least one free magnetic layer.When the magnetic field direction of the free magnetic layer is parallelto the magnetic field direction of the pinned magnetic layer, theelectrical resistance R of the MR sensor is lowest. When reading data, amagnetic data bit of a hard disk will cause the magnetic field directionof the free magnetic layer to change, whereupon the electricalresistance of the sensor increases. This change in resistance (ΔR)affects the electrical current passing through the sensor, which is thusdetected as a data signal.

[0006] It is desirable to develop MR sensors having a decreasedthickness, while maintaining or even increasing the ΔR value. Where themetallic MR sensor layers, and particularly the spacer layer, are madethinner, the electrical resistance of the thinner layers increases andthere is less shunting of electrical current through these layers andaway from the free magnetic layer. This leads to an increase in thesensor resistance R and in ΔR, and this results in improved magnetichead performance. Another parameter that is significant in spin valvesensor performance is the magnetic coupling field strength between thepinned and free magnetic layers, and it is important to maintain thiscoupling field strength to maintain the spin valve performance.

[0007] Many different materials and fabrication steps have been utilizedin the prior art in attempts to increase ΔR of the MR sensor. Thepresent invention relates to a MR spin valve sensor that is fabricatedutilizing a surface smoothed pinned magnetic layer. This allows the useof a thinner spacer layer, thus leading to an increased electricalresistance R of the sensor and a higher ΔR, which correlates to astronger read head signal.

[0008] It has been described in an abstract of prior art paper entitled“Effect of Plasma Treatment on the GMR Properties of PtMn BasedSynthetic Spin Valve,” by K. Tsunekawa, D. Nakagima and N. Watanabe,presented as paper BD-04 at the 46^(th) Annual Conference on Magnetismand Magnetic Materials, in Seattle, Wash., USA on Nov. 12-16, 2001, thatwith respect to a GMR spin valve sensor, that the surface of a pinnedmagnetic layer can be smoothed utilizing a low voltage argon plasma. Acopper spacer layer and a free magnetic layer are then deposited. Theresulting GMR sensor was shown to be improved by having an increasedsignal strength.

[0009] The present invention is an improvement upon this prior art inthat it's utilizes an improved plasma comprised of argon plus oxygen,and that it utilizes an MR head having a CuO_(x) spacer layer betweenthe pinned and free magnetic layers.

SUMMARY OF THE INVENTION

[0010] The magnetic head of the present invention includes a spin valvesensor read head having a sensor layer stack that includes a pinnedmagnetic layer, a spacer layer formed on the pinned magnetic layer, anda free magnetic layer formed on the spacer layer. In a preferredembodiment the spacer layer is comprised of CuO_(x). Improved spin valvesensor properties are obtained by plasma smoothing the upper surface ofthe pinned magnetic layer prior to depositing the spacer layer, and apreferred plasma gas is a mixture of argon and oxygen. The plasmasmoothing of the pinned magnetic layer has the effect of increasing thenegativity of the magnetic coupling field strength between the pinnedand free magnetic layers, and the spacer layer can then be made thinnerto adjust the coupling field strength to its desired value. The reducedthickness of the spacer layer results in increased sensor resistance andan increase in the sensor signal amplitude. In the preferred embodiment,the CuO_(x) spacer thickness is reduced from approximately 20 Å toapproximately 16 Å.

[0011] It is an advantage of the magnetic head of the present inventionthat it includes a magnetoresistive sensor having a decreased sensorspacer layer thickness.

[0012] It is another advantage of the magnetic head of the presentinvention that it includes a magnetoresistive sensor having a decreasedsensor spacer layer thickness, an increased sensor signal amplitude.

[0013] It is a further advantage of the magnetic head of the presentinvention that it includes a CuO_(x) spacer layer disposed upon a pinnedmagnetic layer having a smoothed surface.

[0014] It is yet another advantage of the magnetic head of the presentinvention that it includes a laminated pinned magnetic layer having aplasma smoothed upper surface, with a reduced thickness CuO_(x) spacerlayer disposed thereon, that results in a sensor an increased signalamplitude.

[0015] It is an advantage of the hard disk drive of the presentinvention that it includes a magnetic head of the present invention thatincludes a magnetoresistive sensor having a decreased sensor spacerlayer thickness.

[0016] It is another advantage of the hard disk drive of the presentinvention that it includes a magnetic head of the present invention thatincludes a magnetoresistive sensor having a decreased sensor spacerlayer thickness, an increased sensor signal amplitude.

[0017] It is a further advantage of the hard disk drive of the presentinvention that it includes a magnetic head of the present invention thatincludes a CuO_(x) spacer layer disposed upon a pinned magnetic layerhaving a smoothed surface.

[0018] It is yet another advantage of the hard disk drive of the presentinvention that it includes a magnetic head of the present invention thatincludes a laminated pinned magnetic layer having a plasma smoothedupper surface, with a reduced thickness CuO_(x) spacer layer disposedthereon, that results in a sensor an increased signal amplitude.

[0019] It is an advantage of the method for fabricating a magnetic headof the present invention that it includes a pinned magnetic layer havinga plasma smoothed upper surface and a CuO_(x) spacer layer having areduced thickness, such that increased signal amplitude of the sensorresults.

[0020] The foregoing and other objects, features, and advantages of thepresent invention will be apparent from the following detaileddescription of the preferred embodiments which make reference to theseveral figures of the drawing.

IN THE DRAWINGS

[0021] The following drawings are not made to scale of an actual device,and are provided for illustration of the invention described herein.

[0022]FIG. 1 is a top plan view generally depicting a hard disk drivethat includes a magnetic head of the present invention;

[0023]FIG. 2 is a side cross-sectional view depicting a typical priorart spin valve read head portion of a magnetic head;

[0024]FIG. 3 is a side cross-sectional view depicting typical thin filmlayers that may be utilized in fabricating a first embodiment of thespin valve sensor structure of the present invention;

[0025]FIG. 4 is a graph depicting the performance characteristics of theargon plus oxygen plasma smoothed pinned magnetic layer of the magnetichead of the present invention; and

[0026]FIG. 5 is a graph providing performance data of the magnetic headof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027]FIG. 1 is a top plan view that depicts significant components of ahard disk drive which includes the magnetic head of the presentinvention. The hard disk drive 10 includes a magnetic media hard disk 12that is rotatably mounted upon a motorized spindle 14. An actuator arm16 is pivotally mounted within the hard disk drive 10 with a magnetichead 20 of the present invention disposed upon a distal end 22 of theactuator arm 16. A typical hard disk drive 10 may include a plurality ofdisks 12 that are rotatably mounted upon the spindle 14 and a pluralityof actuator arms 16 having one or more magnetic heads 20 mounted uponthe distal end 22 of the actuator arms. As is well known to thoseskilled in the art, when the hard disk drive 10 is operated, the harddisk 12 rotates upon the spindle 14 and the magnetic head 20 acts as anair bearing slider that is adapted for flying above the surface of therotating disk. The slider includes a substrate base upon which thevarious layers and structures that form the magnetic head arefabricated. Such heads are fabricated in large quantities upon a wafersubstrate and subsequently sliced into discrete magnetic heads 20.

[0028] A typical prior art magnetic head is fabricated to include a readhead portion for reading data from the hard disk and a write headportion for writing to a hard disk, and FIG. 2 is a generalizeddepiction of a prior art read head spin valve portion of a magnetic headwhich will serve as a starting point for the description of the novelread head features of the present invention. As depicted in FIG. 2, thespin valve 30 includes a first magnetic shield layer (S1) 34 that isfabricated upon the surface 38 of a substrate base 42. A firstinsulation layer (G1) 44 is fabricated upon the S1 shield 34 and aplurality of spin valve sensor layers 50 are then fabricated upon the G1layer 44. A detailed description of the sensor layers 50 is providedhereinbelow, and the novel sensor layers of the present invention arethen discussed. Using photolithographic and etching techniques, portionsof the sensor layers are removed such that the central portions 50depicted in FIG. 2 remain. Thereafter, hard bias elements 54 arefabricated next to the sensor layers 50, electrical leads 60 arefabricated upon the hard bias elements 54, a second electricalinsulation layer (G2) 64 is deposited across the device followed by thefabrication of a second magnetic shield (S2) 68, and a write headportion (generally indicated as 72) is subsequently fabricated tocomplete the magnetic head fabrication process.

[0029] The present invention is directed towards improvements in thespecific layers that comprise the sensor layer stack 50 of the spinvalve, and a more detailed depiction of a magnetoresistive (MR) spinvalve sensor, such as may be utilized as an improved sensor 80 of thepresent invention in the magnetic head 20 of FIG. 1 is depicted in FIG.3. As depicted in FIG. 3, a G1 insulation layer 44 typically composed ofAl₂O₃, is fabricated upon the S1 shield layer 34, that may typically becomposed of NiFe. This is followed by the fabrication of the spin valvelayer structure 90, commencing with a seed layer 84 that may be composedof an AlO_(x) sublayer, an NiFeCr sublayer, and a NiFe sublayer.Following the seed layer deposition, the sequence of sensor layers inthe spin valve layer structure 90 includes a PtMn antiferromagneticlayer 94, a CoFe/Ru/CoFe laminated pinned magnetic layer 98, a CuO_(x)spacer layer 102, a CoFe/NiFe free magnetic layer 106, and a Ta caplayer 110, and the typical thickness of the various layers is set forthin FIG. 3.

[0030] Magnetoresistive spin valve sensors, such as are describedherein, operate by detecting magnetic data bits written upon a hard diskthrough a change in electrical resistance within the spin valve sensorwhen the sensor is exposed to the magnetic field of the data bit.Specifically, the orientation of the magnetic field of the free magneticlayer field is altered by the magnetic field of a data bit, and thechange in the orientation of the free layer magnetic field creates achange in the electrical resistance R of the sensor. The electricalresistance of the sensor is lowest (Rmin) when the free layer magneticfield is oriented parallel to the pinned layer magnetic field, and theresistance of the sensor increases when the free layer magnetic field isoriented other than parallel to the pinned layer magnetic fielddirection. This change in resistance R-Rmin is generally designated asΔR. Significantly, the resistance R of the sensor is determined in largepart by the resistance of the spacer layer, and generally a thinnerspacer layer will typically have a higher resistance R, which willgenerally result in a higher value for ΔR, provided themagnetoresistance coefficient ΔR/R remains constant. Another importantparameter in spin valve performance is the strength of the magneticcoupling field between the pinned magnetic layer and the free magneticlayer. This magnetic coupling field is held within a desired range topromote good SV performance, as is described more fully herebelow.

[0031] Therefore, it is a performance goal for the spin valve sensor ofthe present invention to have an increased electrical resistance R andan increased ΔR while maintaining the magnetic coupling field within adesired range, as well as to not negatively affect other sensorproperties such as ΔR/R and coercivity. As will appear from thefollowing description, an improvement in the smoothness of the uppersurface of the pinned magnetic layer results in improved spin valvesensor properties.

[0032] Returning to FIG. 3, the focus of the present invention is on theupper surface 120 of the pinned magnetic layer 98. Specifically, wherethe surface 120 is smooth, the magnetic coupling between the pinned andfree magnetic layers occurs becomes more negative. Then, to adjust themagnetic coupling value back to its original, more desired value, thethickness of the spacer layer 102 can be reduced. Finally, due to thereduced thickness of the spacer layer, the electrical resistance of thespacer layer (and therefore the sensor) is increased, which also createsan increase in ΔR (since ΔR/R remains constant), thereby increasing thesignal amplitude of the sensor signal. It is therefore to be understoodthat the smoothing of the surface of the pinned magnetic layer 98results in a thinner spacer layer 102 and improved sensor performancecharacteristics.

[0033] The effects of smoothing the surface of the pinned magnetic layerof a GMR spin valve sensor having a copper spacer layer have beenreported by others, see “Effect of Plasma Treatment on the GMRProperties of PtMn Based Synthetic Spin Valve,” by K. Tsunekawa, D.Nakagima and N. Watanabe, presented as paper BD-04 at the 46^(th) AnnualConference on Magnetism and Magnetic Materials, in Seattle, Wash., USAon Nov. 12-16, 2000. A low voltage argon plasma was used in this priorart pinned layer smoothing process, with a Cu spacer then beingdeposited upon the argon plasma smoothed surface.

[0034] In a preferred embodiment of the present invention, as depictedin FIG. 3, a CuO_(x) spacer is used in the sensor structure 90, and aplasma process gas of argon plus oxygen is used to perform the surfacesmoothing of the pinned magnetic layer prior to the deposition of thespacer layer. As will be understood by those skilled in the art, themagnetic head sensor fabrication process is conducted in a multi-chamberfabrication device in which one or more wafers are disposed upon a waferchuck, and the wafer chuck is movable into a plurality of chambers inwhich various layers and processes are performed. With reference to thepresent invention, the wafer chuck is moved into successive chamberswhere the various sensor film layers are sequentially deposited,including the S1 shield, the G1 insulation layer, the seed layer, theantiferromagnetic layer, and the pinned magnetic layer. Following thedeposition of the pinned magnetic layer, the plasma process gas isintroduced into the processing chamber and a low bias voltage is appliedto the chuck. A plasma is struck for a short period of time in which thesurface of the pinned magnetic layer is exposed to the plasma, and thesmoothing of the surface is achieved.

[0035] With regard to the surface smoothing process of the presentinvention, the wafer chuck having a wafer with the pinned magnetic layerdeposited thereon is disposed in a process chamber at a pressure of fromapproximately 1×10⁻³ Torr to approximately 3×10⁻³ Torr. The argon plusoxygen plasma gas mixture is introduced at a flow rate of approximately50 sccm and it is comprised of approximately 49.5 sccm pure argon plus0.5 sccm of an 80% argon plus 20% oxygen gas mixture. This correlates toan oxygen partial pressure of approximately 2×10⁻⁶ Torr. It has beendiscovered that an oxygen partial pressure of from 0.5×10⁻⁶ toapproximately 6×10⁻⁶ Torr will provide superior surface smoothingresults. A wafer chuck bias voltage of from approximately 25 toapproximately 70 volts, and preferably from 30 to 60 volts, is used tosupport the plasma, where the plasma striking voltage is approximately25 volts. A surface smoothing plasma exposure time of from approximately15 to approximately 60 seconds is sufficient to achieve the surfacesmoothing effects of the present invention. As will be appreciated bythose skilled in the art, the surface smoothing time exposure is afunction of parameters such as the bias voltage and plasma composition.

[0036] Following the plasma surface smoothing step, the wafer chuck ismoved to a spacer deposition chamber, and a CuO_(x) spacer layer 102 isnext deposited upon the smoothed surface 120 of the pinned magneticlayer 98. The CuO_(x) is deposited at approximately 1 Å per second, thusa deposition time of approximately 16 to 20 seconds is utilized in thepresent invention to obtain a CuO_(x) thickness of approximately 16 to20 Å, with a preferred CuO_(x) thickness being approximately 17 Å.Thereafter, the free magnetic layer and cap layer are sequentiallydeposited.

[0037] The CuO_(x) spacer layer has an increased electrical resistanceas compared to the prior art Cu spacer. Additionally, the properties ofthe CuO_(x) spacer result in a negative magnetic coupling field betweenthe pinned and free magnetic layers. The strength of this coupling fieldis a significant sensor parameter that affects the rotation of themagnetic field of the free magnetic layer and thus the performance ofthe sensor. The strength of the coupling field is affected by thethickness of the spacer layer between the pinned and free magneticlayer, and as is discussed more fully below, it is an important featureof the present invention to maintain the coupling field strength withina desired range, and thereby reduce the thickness of the spacer layer.

[0038] It is therefore to be understood that a key contributor to thecoupling field strength is the nano-scale roughness of the pinned layerspacer layer interface, and as is shown in FIG. 4, a reduction in thisroughness leads to a reduction in coupling field for a given spacerthickness or conversely allows one to reduce the spacer thickness whilemaintaining a given coupling field. A reduction in the spacer thicknessis beneficial in two ways, the ΔR/R of the sensor increases as thespacer becomes thinner, while at the same time the sensor resistance Rbecomes larger. The product of ΔR/R and R is ΔR, which is a good figureof merit for predicting signal amplitude in a read head. As is shown inFIG. 5 and discussed below, this figure of merit and thus the magnetichead signal is improved by reducing the pinned layer surface roughness.

[0039]FIG. 4 is a graph showing the coupling field strength Hf throughthe GMR spacer as a function of the spacer thickness. The spacer isoxygen doped Cu in this case, where it is known that oxygen inclusion inCu is beneficial in reducing the coupling field. The data in squaresymbols shows the coupling field for a normally deposited sensor layerstack with a CuO spacer layer composition. The data in diamond symbolsshows the coupling field reduction due to plasma smoothing using argongas only. Finally the data in triangle symbols shows a further couplingfield reduction when using an argon plus oxygen plasma. It can thereforebe seen that without plasma smoothing (square symbols) that the couplingfield strength range of −5 to −15 Oe is achieved with a CuO_(x) spacerthickness of approximately 19 Å, and that with an argon plasma smoothing(diamond symbols) that the coupling field strength of −5 to −15 Oe isachieved with a CuO_(x) spacer thickness of approximately 18 Å. Thepreferred plasma smoothing of the present invention using an argon plusoxygen plasma (triangle symbols) and a CuO_(x) spacer layer with acoupling field strength of −5 to −15 Oe results in a spacer layerthickness of approximately 17 Å. It is apparent from these curves thatthese plasma treatments considerably enlarge the process window fornegative coupling. Thus, plasma smoothing can be employed to reduce thespacer thickness while keeping a fixed coupling field value.

[0040]FIG. 5 is a graph showing how the figure of merit (ΔR, which isequal to ΔR/R times sheet resistance (R)) varies with the CuO_(x) spacerthickness. The data in square symbols shows the ΔR values for a normallydeposited sensor layer stack with a CuO spacer layer composition. Thedata in diamond symbols shows the ΔR values due to plasma smoothingusing argon gas only. Finally the data in triangle symbols shows the ΔRvalues when using an argon plus oxygen plasma. It can therefore be seenthat generally ΔR increases as the CuO_(x) spacer layer thickness isreduced. Thus, the present invention allows the deposition of a thinnerspacer layer and thus an increase in ΔR which corresponds to improvedGMR sensor performance.

[0041] The spin valve sensor of the present invention is an improvementover the prior art described above, in that the smoothing of the surfaceof the pinned magnetic layer is conducted utilizing a plasma gas mixturecomprising argon plus oxygen, and also in that the spacer layer iscomprised of CuO_(x) instead of Cu. Each of these changes results in animprovement over the prior art, and when combined together in apreferred embodiment of the present invention, they create a furtherimproved device.

[0042] While the present invention has been shown and described withregard to certain preferred embodiments, it is to be understood thatthose skilled in the art will no doubt develop certain alterations andmodifications in form and detail therein. It is therefore intended thatthe following claims cover all such alterations and modifications thatnevertheless include the true spirit and scope of the present invention.

What I claim is:
 1. A magnetic head including a spin valve sensorcomprising: a pinned magnetic layer, a spacer layer disposed upon saidpinned magnetic layer, and a free magnetic layer disposed upon saidspacer layer; and wherein said pinned magnetic layer is formed with anupper surface that is smoothed by an argon plus oxygen plasma and saidspacer layer is disposed upon said smoothed upper surface of said pinnedmagnetic layer.
 2. A magnetic head as described in claim 1 wherein saidspacer layer is comprised of Cu.
 3. A magnetic head as described inclaim 1 wherein said spacer layer is comprised of CuO_(x).
 4. A magnetichead as described in claim 3 wherein said pinned magnetic layer iscomprised of CoFe.
 5. A magnetic head as described in claim 3 whereinsaid free magnetic layer is comprised of NiFe.
 6. A magnetic head asdescribed in claim 3 wherein said pinned magnetic layer is comprised ofa laminated structure including layers of CoFe, Ru, and CoFe.
 7. Amagnetic head as described in claim 3 wherein said free magnetic layeris comprised of a laminated structure including layers of CoFe and NiFe.8. A magnetic head including a spin valve sensor comprising: a magneticshield layer (S1) being fabricated above a substrate base; a firstelectrical insulation layer (G1) being fabricated above said S1 layer; aspin valve sensor structure being disposed above said G1 layer; whereinsaid spin valve sensor structure includes a seed layer being fabricatedabove said G1 layer, an antiferromagnetic layer being disposed abovesaid seed layer, a pinned magnetic layer being disposed above saidantiferromagnetic layer, a spacer layer being disposed upon said pinnedmagnetic layer, and a free magnetic layer being disposed upon saidspacer layer; and wherein said pinned magnetic layer is formed with aplasma smoothed upper surface and said spacer layer is comprised ofCuO_(x).
 9. A magnetic head as described in claim 8, wherein a magneticcoupling field exists across said spacer layer having a coupling fieldstrength of from approximately −5 Oe to approximately −15 Oe, and saidspacer layer is formed with a thickness of from approximately 16 Å toapproximately 20 Å.
 10. A magnetic head as described in claim 9 whereinsaid coupling field strength is approximately −10 Oe, and said spacerthickness is approximately 17 Å.
 11. A magnetic head as described inclaim 9 wherein said pinned magnetic layer is comprised of CoFe.
 12. Amagnetic head as described in claim 9 wherein said free magnetic layeris comprised of NiFe.
 13. A magnetic head as described in claim 9wherein said pinned magnetic layer is comprised of a laminated structureincluding layers of CoFe, Ru, and CoFe.
 14. A magnetic head as describedin claim 9 wherein said free magnetic layer is comprised of a laminatedstructure including layers of CoFe and NiFe.
 15. A hard disk driveincluding a magnetic head including a spin valve sensor comprising: amagnetic shield layer (S1) being fabricated above a substrate base; afirst electrical insulation layer (G1) being fabricated above said S1layer; a spin valve sensor structure being disposed above said G1 layer;wherein said spin valve sensor structure includes a seed layer beingfabricated above said G1 layer, an antiferromagnetic layer beingdisposed above said seed layer, a pinned magnetic layer being disposedabove said antiferromagnetic layer, a spacer layer being disposed uponsaid pinned magnetic layer, and a free magnetic layer being disposedupon said spacer layer; and wherein said pinned magnetic layer is formedwith a plasma smoothed upper surface and said spacer layer is comprisedof CuO_(x).
 16. A hard disk drive including a magnetic head as describedin claim 15, wherein a magnetic coupling field exists across said spacerlayer having a coupling field strength of from approximately −5 Oe toapproximately −15 Oe, and said spacer layer is formed with a thicknessof from approximately 16 Å to approximately 20 Å.
 17. A hard disk driveincluding a magnetic head as described in claim 16 wherein said couplingfield strength is approximately −10 Oe, and said spacer thickness isapproximately 17 Å.
 18. A hard disk drive including a magnetic head asdescribed in claim 15 wherein said pinned magnetic layer is comprised ofCoFe.
 19. A hard disk drive including a magnetic head as described inclaim 15 wherein said free magnetic layer is comprised of NiFe.
 20. Ahard disk drive including a magnetic head as described in claim 15wherein said pinned magnetic layer is comprised of a laminated structureincluding layers of CoFe, Ru, and CoFe.
 21. A hard disk drive includinga magnetic head as described in claim 15 wherein said free magneticlayer is comprised of a laminated structure including layers of CoFe andNiFe.
 22. A method for fabricating a magnetic head including a readsensor, including the steps of: depositing a pinned magnetic layer;smoothing an upper surface of said pinned magnetic layer utilizing anargon plus oxygen plasma; depositing a spacer layer upon said uppersurface of said pinned magnetic layer; depositing a free magnetic layerupon said spacer layer.
 23. A method for fabricating a magnetic head asdescribed in claim 22 wherein said argon plus oxygen plasma includesoxygen in a concentration of from approximately 0.05% to approximately0.6%.
 24. A method for fabricating a magnetic head as described in claim22 wherein said argon plus oxygen plasma is used with a pressure of fromapproximately 1×10⁻³ Torr to 3×10⁻³ Torr, and the partial pressure ofoxygen is from approximately 0.5×10⁻⁶ Torr to 6×10⁻⁶ Torr.
 25. A methodfor fabricating a magnetic head as described in claim 24 wherein saidspacer layer is formed with a thickness of from approximately 16 Å toapproximately 20 Å.
 26. A method for fabricating a magnetic head asdescribed in claim 22 wherein a magnetic coupling field exists acrosssaid spacer layer having a coupling field strength of from approximately−5 Oe to approximately −15 Oe, and said spacer layer is formed with athickness of from approximately 16 Å to approximately 20 Å.
 27. A methodfor fabricating a magnetic head as described in claim 26 wherein saidargon plus oxygen plasma is used with a pressure of from approximately1×10⁻³ Torr to 3×10⁻³ Torr, and the partial pressure of oxygen is fromapproximately 0.5×10⁻⁶ Torr to 6×10⁻⁶ Torr.
 28. A method for fabricatinga magnetic head as described in claim 27 wherein said spacer layer isformed with a thickness of from approximately 16 Å to approximately 20Å.